This research will encompass studies of a pineal antigonadotropic substance having peptidic characteristics. In view of its potential anti-LH properties observed in rats, I propose to study the effects of the pineal antigonadotropin on fertility in rats. The overall objective will be to further characterize the biological response to the pineal antigonadotropin and study the efficacy of the purified material as an antifertility agent. The material will be prepared from bovine pineal glands by aqueous extraction and purified by gel-filtration and thin layer chromatography. The identity and activity of the material will be determined by its ability to inhibit the post-castration rise of LH in male rats. The antigonadotropin will be used initially in three experimental models to determine its efficacy on the inhibition of ovulation, implantation, and term-pregnancy in rats. By varying dose and schedule of treatment, the minimum effective dose will be determined for either blocking or altering one or more of these events. Where results are positive in these initial experiments, I will then measure the alteration of blood levels of LH, prolactin, 17 beta-estradiol, estrone and progesterone by radio-immunoassay at the time the material is most effective. The critical hypothesis is that the preovulatory and preimplantation rise of LH and the LH titers during pregnancy can be reduced or abolished and that by this means the pineal peptide will be effective as an antifertility agent. If this hypothesis proves true, the compound's peptidic nature provides the possibility of complete structural identity, synthesis and, after appropriate testing in lower animals, extend the possibility for development of a new contraceptive method.